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Julius Werner 2b23948535 gpio: Add support for binary_first base3 number system
This patch adds support for an alternative ternary number system in
which group of GPIOs can be interpreted. In this system, the digit
combinations that would form a binary number (i.e. that contain no 'Z'
state) are used to represent the lower values in the way they're used in
the normal binary system, and all the combinations that do contain a 'Z'
are used to represent values above those. We can use this for boards
that originally get strapped with binary board IDs but eventually
require more revisions than that representation allows. We can switch
their code to binary_first base3 and all old revisions with already
produced boards will still get read as the correct numbers.

Credit for the algorithm idea goes to Haran Talmon.

BRANCH=None
BUG=None
TEST=Stubbed out the actual GPIO reading and simulated all combinations
of 4 ternary digits for both number systems.

Change-Id: Ib5127656455f97f890ce2999ba5ac5f58a20cf93
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://review.coreboot.org/14116
Tested-by: build bot (Jenkins)
Reviewed-by: David Hendricks <dhendrix@chromium.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
2016-03-22 21:18:30 +01:00
3rdparty vboot: Update to current master to support S3 resume signalling 2016-02-29 20:19:06 +01:00
Documentation Documentation: x86 MTRR setup, TempRamExit and MTRR loading 2016-03-21 20:12:35 +01:00
payloads payloads: Add a target to print payload git urls and directories 2016-03-21 14:32:02 +01:00
src gpio: Add support for binary_first base3 number system 2016-03-22 21:18:30 +01:00
util rockchip: update make_idb.py 2016-03-16 15:24:10 +01:00
.clang-format
.gitignore payloads: Enable building depthcharge as part of the coreboot build 2016-03-15 21:18:22 +01:00
.gitmodules git modules: rename git submodules to avoid hierarchies 2016-02-11 20:55:55 +01:00
.gitreview
COPYING
MAINTAINERS MAINTAINERS: Add maintainer for Braswell SOC & Reference board 2016-03-22 19:58:35 +01:00
Makefile Makefile: Update payload clean targets 2016-03-09 17:01:56 +01:00
Makefile.inc build system: Allow overriding the path to the futility binary 2016-03-17 15:38:47 +01:00
README
toolchain.inc toolchain.inc: test IASL by version string instead of number 2016-03-04 16:36:25 +01:00

README

-------------------------------------------------------------------------------
coreboot README
-------------------------------------------------------------------------------

coreboot is a Free Software project aimed at replacing the proprietary BIOS
(firmware) found in most computers.  coreboot performs a little bit of
hardware initialization and then executes additional boot logic, called a
payload.

With the separation of hardware initialization and later boot logic,
coreboot can scale from specialized applications that run directly
firmware, run operating systems in flash, load custom
bootloaders, or implement firmware standards, like PC BIOS services or
UEFI. This allows for systems to only include the features necessary
in the target application, reducing the amount of code and flash space
required.

coreboot was formerly known as LinuxBIOS.


Payloads
--------

After the basic initialization of the hardware has been performed, any
desired "payload" can be started by coreboot.

See http://www.coreboot.org/Payloads for a list of supported payloads.


Supported Hardware
------------------

coreboot supports a wide range of chipsets, devices, and mainboards.

For details please consult:

 * http://www.coreboot.org/Supported_Motherboards
 * http://www.coreboot.org/Supported_Chipsets_and_Devices


Build Requirements
------------------

 * make
 * gcc / g++
   Because Linux distribution compilers tend to use lots of patches. coreboot
   does lots of "unusual" things in its build system, some of which break due
   to those patches, sometimes by gcc aborting, sometimes - and that's worse -
   by generating broken object code.
   Two options: use our toolchain (eg. make crosstools-i386) or enable the
   ANY_TOOLCHAIN Kconfig option if you're feeling lucky (no support in this
   case).
 * iasl (for targets with ACPI support)

Optional:

 * doxygen (for generating/viewing documentation)
 * gdb (for better debugging facilities on some targets)
 * ncurses (for 'make menuconfig' and 'make nconfig')
 * flex and bison (for regenerating parsers)


Building coreboot
-----------------

Please consult http://www.coreboot.org/Build_HOWTO for details.


Testing coreboot Without Modifying Your Hardware
------------------------------------------------

If you want to test coreboot without any risks before you really decide
to use it on your hardware, you can use the QEMU system emulator to run
coreboot virtually in QEMU.

Please see http://www.coreboot.org/QEMU for details.


Website and Mailing List
------------------------

Further details on the project, a FAQ, many HOWTOs, news, development
guidelines and more can be found on the coreboot website:

  http://www.coreboot.org

You can contact us directly on the coreboot mailing list:

  http://www.coreboot.org/Mailinglist


Copyright and License
---------------------

The copyright on coreboot is owned by quite a large number of individual
developers and companies. Please check the individual source files for details.

coreboot is licensed under the terms of the GNU General Public License (GPL).
Some files are licensed under the "GPL (version 2, or any later version)",
and some files are licensed under the "GPL, version 2". For some parts, which
were derived from other projects, other (GPL-compatible) licenses may apply.
Please check the individual source files for details.

This makes the resulting coreboot images licensed under the GPL, version 2.